Related by context. Frequent words. (Click for all words.) 60 landforms 59 volcanism 58 mass extinctions 57 meteoroids 57 cometary 57 Volcanic eruptions 56 ejecta 56 marine sediments 56 plate tectonics 56 volcanic eruptions 56 meteoroid 56 galaxy formation 56 Earth magnetosphere 56 methane hydrates 55 polar caps 55 abiotic 55 comets 55 lithosphere 55 aerosol particles 55 supernova explosion 55 Saturn moons 55 terrestrial ecosystems 55 landmasses 55 olivine 54 meteorites 54 rocky planets 54 earths 54 moon Europa 54 terrestrial planets 54 subduction zones 54 silicates 54 glaciation 53 supernova explosions 53 asteroids 53 astrobiologists 53 marine reptiles 53 Saturn rings 53 primordial 53 martian 53 interstellar dust 53 planets 53 icecaps 53 crustal 53 outer planets 52 primordial soup 52 organic molecules 52 hydrological cycle 52 equatorial regions 52 cosmic ray 52 habitable planets 52 Saturn moon 52 craters 52 magnetosphere 52 depressions 52 oceanic crust 52 radioactive decay 52 vortexes 51 hydrothermal 51 X ray emission 51 oxygen isotopes 51 glacial melt 51 nucleation 51 quark gluon plasma 51 regolith 51 Kuiper belt 51 mid latitudes 51 spacetime 51 Titan Saturn 51 megafauna 51 morphologies 51 lunar poles 51 scarps 51 Martian surface 51 super Earths 51 planetary 50 earth crust 50 martian surface 50 single celled organisms 50 galaxy clusters 50 lava flows 50 scientists theorize 50 multicellular organisms 50 interstellar medium 50 micrometeorites 50 dust devils 50 calcite 50 microscopic organisms 50 cosmological 50 volcanic activity 50 waterspouts 50 cosmic rays 50 cosmic radiation 50 methane hydrate 50 geologically active 50 elliptical galaxies 50 cosmic 50 gravitational waves 50 magmatic 49 Enceladus 49 perturbations 49 retreating glaciers